1. Field of the Invention
The present invention relates to a method and an apparatus for controlling the operaton of an engine in an engine characteristics test to be performed in an experimental room.
2. Description of the Background Art
A test of engine characteristics such as engine noise or amount of exhaust is usually conducted inside an experimental room, because of the difficulty of collecting data on a running car, which is carrying engine.
In such a test, engine axial torque and a rotational speed are controlled at prescribed values by adjusting throttle valve opening of the engine and dynamometer current of dynamometer associated with the engine.
An example of a conventional apparatus for performing such an engine test is shown in FIG. 1.
In this apparatus, an operator enters reference values for the axial torque and the rotational speed at operation command generator 1, and reference signals indicating these reference values are subsequently output to substractors 4a and 4b.
Meanwhile, an engine 2 to be tested is equipped with a rotational speed detector 3 from which a measured value for the rotational speed is fed back to the substractor 4a, so that the subtractor 4a calculates a difference between the measured value and the reference value for the rotational speed.
This difference obtained by the subtractor 4a is then fed to an engine controller 5 which performs a control operation to nullify the difference by generating a throttle valve control signal to appropriately adjust a throttle controller 6 connected to a throttle valve (not shown) of the engine 2.
On the other hand, the engine 2 is also equipped with an axial torque detector 7 from which a measured value for the axial torque is fed back to the substractor 4b, so that the subtractor 4b calculates a difference between the measured value and the reference value for the axial torque.
This difference obtained by the subtractor 4b is then fed to a dynamometer controller 8 which performs a control operation to nullify the difference by generating dynamometer current control signal to appropriately adjust dynamometer current controller 9 connected to a dynamometer 10.
In this manner, the rotational speed and the axial torque of the engine 2 are adjusted in correspondence with various driving conditions, such that the data concerning characteristics of the engine 2 under various driving conditions can be obtained.
However, in such a conventional apparatus for performing an engine test, the system for controlling the rotational speed by the adjustment of the throttle valve opening, and the system for controlling the axial torque by adjusting the dynamometer current are completely independent of each other. In other words, each system is operating as a single-input single-output system, so that it has been impossible to control these systems with mutual interference between these systems taken into account. For this reason, it has been difficult to stabilize the rotational speed and the axial torque simultaneously, so that a highly accurate test of engine characteristics has been impossible.